Coatings containing drying oils and their fatty acid derivatives, as alkyds, dry by oxidative cross-linking. Driers are added to air-drying coating systems to accelerate or promote, after application, the transformation from the liquid film into the solid stage within appropriate time. Different metal driers have different drying properties as some metals have much more catalytic effect than others. Driers are commonly divided into two main classes according to their catalytic activity. The primary driers have some catalytic effect, whereas the secondary driers have no catalytic effect at all. Cobalt carboxylates are the most widely used driers in solvent-based alkyd paints. They are used for their high efficiency but the toxicity of cobalt is their disadvantage. In the context of new legislative provisions, alternative Co-free driers are searched.
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